Field of Invention
The present invention relates to a vehicle having a steering brake system, in particular a steering brake locking system for such a vehicle.
Description of Related Art
Some vehicles, and in particular agricultural tractors, are regularly provided with steering brake systems. Such systems generally comprise independent brake circuits for different wheels of the vehicle, e.g. left and right rear wheels, to allow the driver to brake only the inside wheel during a turning operation. This provides tighter turning circles, allowing for greater control of vehicle movement.
Such steering brake systems generally comprise separate brake pedals to separately control the braking actions of the different wheels. In addition, the pedals are often provided with a pedal locking system such that the pedals may be locked together for combined actuation of the wheel brakes. This avoids the risk of single wheel braking at high speeds, e.g. on a highway, which could result in undesired swerving of the vehicle. An example of a prior art steering brake system is provided in EP 2376317 B1, which describes the use of dedicated sensors to determine whether one or both brake pedals are actuated, and to indicate to a driver the unlocked state.
The new EU “Mother Regulation” requires increased control of vehicle braking systems, to reduce the risk of accidents. In a particular aspect, the Mother Regulation will require that the maximum speed of a vehicle is limited when steering brake pedals are unlocked, thereby eliminating the risk of single wheel braking at high speeds.
In an effort to satisfy the requirements of the Mother Regulation, it has been suggested to incorporate dedicated sensor systems, e.g. pressure switches, position sensors, optical detector switches, etc., into the design of the steering brake pedals, to detect the locking status of the pedals. Such dedicated sensor systems may then be provided with communication systems to communicate with the vehicle engine control unit (ECU) to regulate the vehicle operation.
However, the use of such dedicated sensor systems to detect locking status of brake pedals requires additional resources in the form of extra components for use in vehicle manufacture. Such components must be resilient enough to survive operational conditions in the area of the brake pedals, which may be exposed to a relatively high level of mud or other debris. In addition, the incorporation of such new sensor systems into existing pedal systems requires additional cab space to physically accommodate the new components, and/or redesign of the existing systems to incorporate the new sensor configuration.